Unless controlled, the water in swimming pools, spas, hot tubs, and the like can become contaminated with algae and similar organisms. The contaminant growth is usually controlled by the addition of a suitable biocide to the water. Typically, the biocide is a halogen derived from solution of a halogen salt; most commonly the halogen salt is a source of chlorine. The amount of chlorine required to maintain the water in a substantially organism-free state depends on the size of the pool or spa, the climatic conditions, the temperature of the water, and the extent of use of the pool or spa. The hot water found in spas and hot tubs necessitates the frequent addition of chlorine, because the material added rapidly loses effectiveness. A device that can be placed in the water to dispense chlorine in controlled amounts relieves the spa or pool owner or operator of the necessity of regularly monitoring and maintaining the chlorine content of the water.
Chlorine dispensing devices exist for swimming pools. One such device, among many, is the Rainbow Plastics Model 330 floating dispenser for solid chlorine. This dispenser resembles an inverted hollow truncated cone. The interior serves as a receptacle into which granular pellets of water-soluble chlorine source material are placed. Around the circumference of the receptacle adjacent to the bottom there are apertures consisting of elongated vertical slots. The slots cooperate with a similarly slotted sleeve which is captive to and rotatable about the exterior of the container. The sleeve can be adjusted so that the slots are fully closed, fully opened, or in between. The top of the receptacle is closable by a lid which does not make an air-tight seal with the receptacle. The walls of the container are hollow and are filled with closed-cell plastic foam. The cavity in which the foam is located is hermetically sealed. The dispenser does not incorporate any ballast elements.
When filled with a soluble solid source of chlorine or other desired halogen ion source and floated in a swimming pool, the pool water enters into the receptacle and fills it to the level at which the dispenser is floating. The water in the receptacle wets at least that source material which lies below the floating waterline of the dispenser. Accordingly, the wetted source material in the receptacle is dissolved thereby releasing the active constituent of the material into the water in the dispenser. The rate at which such solution is released to the adjacent pool or spa is regulated by the extent to which the apertures in the receptacle are opened or closed by the position of the adjustment sleeve on the exterior of the receptacle. However, this dispenser is not conveniently usable in the comparatively small water volume in a spa because the effective size of the apertures of the dispenser cannot be regulated precisely enough to prevent the dispenser from over-chlorinating the spa water which, by reason of its temperature, acts more rapidly on the source material than the usually cooler water in a swimming pool. Also, this dispenser has a relatively large capacity for containing the source material so that, even when its apertures are very nearly closed, substantial quantities of source material are wetted, dissolved and released from the dispenser.
Another chlorine dispensing device for dispensing a soluble solid source of chlorine i.e., for spas and hot tubs is disclosed in U.S. Pat. No. 4,630,634. Rainbow Plastics Model 335 floating dispenser conforms to the disclosure of that patent. That dispenser comprises a tubular body having a hollow pancake-shaped float at a closed upper end of the body and a tubular-shaped sleeve that fits over the opposite open end of the body. The body accommodates a predetermined volume of soluble solid halogen source material, of which a preselected amount is exposed to contact with the water via a plurality of elongated slots or apertures positioned at diametrically opposite locations in the sleeve. The body and sleeve are threadably engagable with one another to form the assembled dispensing device and are placed in the water in a vertically oriented position with the apertures immersed. The pancake-shaped float at the physical top of the body and a lead weight at the bottom of the sleeve ensures that the dispenser floats vertically erect.
The extent of the solid source material that is wetted is controlled by the axial position of the sleeve on the body. That axial position of the sleeve on the body determines the effective area of the vertical slots in the sleeve which afford communication from the bottom of a chamber in the body and sleeve and in which the source material is contained. Only that portion of the source material that lies below the open end of the body and into the sleeve is exposed to the water to form a biocidal solution. The rate that the solution is dispensed to the water outside the dispenser is controlled by the degree of closure of the apertures. The source material in the chamber above the lower end of the body is dry in the chamber because it lies within an air bubble which is trapped in the interior of the body.
It has been discovered that, in some applications, this latter dispenser does not afford sufficient control over the dispensation rate of the solution from the dispenser. The relatively large openings in the dispenser sleeve can permit the passage of solid chlorine granules from the device to the water where such a highly concentrated oxidizing source can discolor adjacent pool or spa surfaces.
Additionally, once the solid halogen source is completely dissolved, the latter dispenser must be reloaded by disassembling the sleeve from the body and loading the new source material into the body. The need to disassemble the dispenser when reloading it can result in loss of the desired operating position adjustment of the sleeve on the body. An advantage of that latter dispenser over the former one is that, in the latter dispenser, only a small controllable position of the source material is wetted when the filled dispenser is placed into a pool or spa.
Other available products include cumbersome floating structures, which receive a non-refillable disposable replaceable cartridge that contains the soluble source of chlorine or other halogen. The exterior of the cartridge contains ribs which cooperate with slots in a large float to hold the cartridge in a selected position vertically relative to the float. The containers are molded with bumps axially spaced along the container adjacent to the bottom end and a single bump adjacent to the top end. The user cuts off one or more bottom bumps to define the extent to which water communicates with the inside of the container, and cuts off the top bump to provide air communication to the inside of the container. The container is then placed into the large float and the resulting assembly is placed in the pool. Water then fills the cartridge to the water line of the floating assembly; the vertical position of the cartridge in the float determines the extent to which the cartridge contents are wetted.
There are several practical difficulties with these last products. They are quite large and so do not fit well into a spa or hot tub. Their size makes them cumbersome to remove from the spa when the spa is to be used. They are aesthetically unappealing. They cannot reliably be adjusted to provide the precise solution rates needed for efficient chlorination (halogenation) of spas and hot tubs because of the crude and imprecise manner in which communication of water to the interior of the cartridge is provided. They are essentially floating packages of halogen source material designed by major source material manufacturers whose purpose is to market source material; the user cannot change source material without changing the entire dispenser; the user cannot use any source material he wishes.
In a dispenser for spas, it is important that the rate of solution of the source material be controllable with meaningful precision over a range commensurate with the lower chlorination requirements of spas, as compared to swimming pools. It is therefore desirable that a dispensing device afford good control over the rate at which a concentrated biocidal solution is created within the dispenser and over the rate at which that solution is dispensed to the exterior of the device. It is desirable that the dispensing device not be too bulky and not create an obstruction in the spa, and be aesthetically pleasing. The dispensing device should be constructed in a manner facilitating source material reloading without having to disassemble the device or disturb the adjustment for controlling the rate of solution dispensation from the interior of the device. The dispensing device should enable the user to select, as he chooses, from among many commercially available source materials. Finally, the dispensing device should be made of a material resistant to damage from prolonged exposure to sunlight and chemicals.